类型安全：从对象取消选中投射 [英] Type safety: Unchecked cast from Object

问题描述

我尝试将一个对象投射到我的Action类，但会产生一个警告：

I try to cast an object to my Action class, but it results in a warning:

Type safety: Unchecked cast from Object to Action<ClientInterface>

Action<ClientInterface> action = null;
try {
 Object o = c.newInstance();
 if (o instanceof Action<?>) {
  action = (Action<ClientInterface>) o;
 } else {
  // TODO 2 Auto-generated catch block
  throw new InstantiationException();
 }
 [...]

感谢您的帮助

Thank you for any help

推荐答案

是的 - 这是 type erasure 。如果 o 实际上是不会被演员捕获的 Action< String> 只有当你尝试使用它，传递一个 ClientInterface 而不是一个字符串。

Yes - this is a natural consequence of type erasure. If o is actually an instance of Action<String> that won't be caught by the cast - you'll only see the problem when you try to use it, passing in a ClientInterface instead of a string.

使用以下命令移除警告：

You can get rid of the warning using:

@SuppressWarnings("unchecked")

作为函数注释，但是你不能很容易地解决基本问题：（

as a function annotation, but you can't easily sort out the underlying problem :(

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